SOLUTION: A piece of wire 30 cm long is cut into two pieces. One of these is bend into a circle, and the other is bent into a square enclosing the circle. What is the diameter of the circle?

Algebra ->  Equations -> SOLUTION: A piece of wire 30 cm long is cut into two pieces. One of these is bend into a circle, and the other is bent into a square enclosing the circle. What is the diameter of the circle?      Log On


   



Question 766778: A piece of wire 30 cm long is cut into two pieces. One of these is bend into a circle, and the other is bent into a square enclosing the circle. What is the diameter of the circle?
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
First focus on either the radius of the circle or the side length of the square. I will choose the circle's radius. You know that later, you must deal with the sum of their perimeters.

Let r=radius of circle. The square that perfectly is circumscribed around it has side 2r. Draw this situation so you can visualize well.

"perimeter" or circumference of the circle is 2%2Api%2Ar.
Perimeter of the square is 4%2A%282r%29.

The original wire length is 30 cm. The total length of wire forming this circle and square must be the sum of their perimeters.

highlight%282%2Api%2Ar%2B4%282%2Ar%29=30%29, find r. THEN find 2%2Ar which is the diameter.

STEPS FROM THAT...
r%282%2Api%2B8%29=30
r%28pi%2B4%29=15
r=15%2F%28pi%2B4%29
..
.